If the East side is a JPanel, and you want to remove it, you could just remove the JPanel from the JFrame...
Here is something I found from another site... :
"the easiest way to remove a component (panel) from a container (frame) is to keep a reference to it, and then call Container.remove(Component) ie:
i haven't tested this code but it should work.
"

“Don’t worry if it doesn’t work right. If everything did, you’d be out of a job.” (Mosher's Law of Software Engineering)
“If debugging is the process of removing bugs, then programming must be the process of putting them in.” (Edsger Dijkstra)